OFFSET
1,2
LINKS
Ivan Panchenko, Table of n, a(n) for n = 1..1000
FORMULA
Equals 1/2 + ( Pi/sqrt(2) ) /tanh( Pi/sqrt(2) ) /2.
Equals 1 + Sum_{k>=1} (-1)^(k+1)*zeta(2*k)/2^k. - Amiram Eldar, Jun 17 2023
EXAMPLE
1.6371602671179672464372644958005735739372633684506946192622824199...
MATHEMATICA
RealDigits[1/2 + Pi/Sqrt[2]/Tanh[Pi/Sqrt[2]]/2, 10, 90][[1]]
PROG
(PARI) sumnumrat(1/(2*x^2+1), 0) \\ Charles R Greathouse IV, Jan 20 2022
(PARI) 1/2 + Pi/sqrt(2)/tanh(Pi/sqrt(2))/2 \\ Charles R Greathouse IV, Jan 20 2022
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
Bruno Berselli, Dec 02 2013
STATUS
approved